Deepwater Barreleye Fish Sports A Clear Canopy

The barreleye (Macropinna microstoma) has extremely light-sensitive eyes that can rotate within a transparent, fluid-filled shield on its head. In this image, although the barreleye is facing downward, its eyes are still looking straight up. This barreleye is about 6 inches (14 cm) long. The fish's tubular eyes, well inside the head, are capped by bright green lenses. The eyes point upward (as shown here) when the fish is looking for food overhead. They point forward when the fish is feeding. The two spots above the fish's mouth are not eyes: those are olfactory organs called nares, which are analogous to human nostrils. Image Credit: © 2004 MBARI

Deepwater Barreleye Fish Sports A Clear Canopy

Imagine, if you will, the ability to have a line of sight directly behind you as you walk down the street.

If a human were built like a Barreleye Fish, a strata of clear liquid and transparent skin at about ear level would replace hair, bone and flesh-tone skin and the eyes would be able to swivel 180 degrees. Bingo ... rear-view vision.

The Barreleye has a clear membrane skin cover for its forehead region and the upper front part of the fish's head is filled with a clear fluid. The eyes are set back inside and are positioned to be able to look forward, but more importantly, look up and see the light given off by deep water creatures as they ply the deep ocean trenches of our Oblate Spheroid.

Bruce Robison and Kim Reisenbichler of the Monterey Bay Aquarium Research Institute use videos from the institute's remotely operated vehicles (ROVs) to study barreleyes off Central California. At depths of 2,000 to 2,600 feet (600 to 800 meters), the ROV cameras typically showed these fish hanging motionless in the water, their eyes glowing a vivid green in the ROV's bright lights. The video also revealed a previously undescribed feature of these fish — its eyes are surrounded by a transparent, fluid-filled shield that covers the top of the fish's head. [double-click image to launch video of the Barreleye fish in action] Image Credit: © 2004 MBARI

This excerpted and edited from LiveScience -

Strange Fish Has See-Through Head
By LiveScience Staff - posted: 23 February 2009 03:01 pm ET

A bizarre deep-water fish called the barreleye has a transparent head and tubular eyes. Since the fish's discovery in 1939, biologists have known the eyes were very good at collecting light. But their shape seemed to leave the fish with tunnel vision.

Now scientists say the eyes rotate, allowing the barreleye to see directly forward or look upward through its transparent head.

The barreleye (Macropinna microstoma) is adapted for life in a pitch-black environment of the deep sea, where sunlight does not reach. They use their ultra-sensitive tubular eyes to search for the faint silhouettes of prey overhead.

Scientists had thought the eyes were fixed in an upward gaze, however. This would make it impossible for the fish to see what was directly in front of them, and very difficult for them to capture prey with their small, pointed mouths.
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Most existing descriptions and illustrations of this fish do not show its fluid-filled shield, probably because this fragile structure was destroyed when the fish were brought up from the deep in nets.
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Barreleyes, just a few inches long, are thought to eat small fishes and jellyfish. The green pigments in their eyes may filter out sunlight coming directly from the sea surface, helping the barreleye spot the bioluminescent glow of jellies or other animals directly overhead. When it spots prey (such as a drifting jelly), a barreleye rotates its eyes forward and swims upward, in feeding mode.
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